Wilms' tumor occurs rarely in adults, especially after the third decade. In adults, the prognosis of Wilms' tumor is worse than in children. In this case report, we present a 48-year old patient who relapsed with advanced stage shortly after primary surgery. A definitive treatment plan has not been established because of the rarity of this tumor in adults. After surgical removal, multimodal therapy should be begun immediately for long-lasting, complete remission.